JP2763259B2 - Manufacturing method of radial anisotropic rare earth magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an R-Fe-B based radially anisotropic rare earth sintered magnet.

[0002]

2. Description of the Related Art Anisotropic magnets formed by finely pulverizing crystalline magnetic anisotropic materials such as ferrite and rare earth alloys and pressing them in a specific magnetic field are used for speakers, motors, measuring instruments, and other electric equipment. Widely used as. Of these, rare earth sintered magnets having anisotropy in the radial direction in particular have excellent magnetic properties and can be freely magnetized in the axial direction. Since they do not need to be reinforced like segment magnets, they are used for AC servomotors, DC brushless motors, etc. In particular, in recent years, a long radial anisotropic magnet has been demanded as the performance of a motor becomes higher. A sintered magnet having a radial orientation is obtained by molding with a mold having a radial orientation at the time of molding in a magnetic field, and is finely pulverized into a magnet alloy powder (hereinafter referred to as a magnetic powder) in a molding portion 6 in the mold as shown in FIG. ), A coil forms a magnetic field in the direction of the arrow. FIG.
FIG. 2 shows the state (arrow) of the magnetic field orientation in the AA ′ section of FIG.
It is shown in a plan sectional view. As shown in FIG. 2, a magnetic field in the radial direction can be obtained in the mold 1 from the core 2 and then compression molded to obtain a radially anisotropic molded body.

[0003] The orientation magnetic field of the mold is determined by the outer periphery, the inner periphery, and the height of the mold, and is expressed by equation (1). k = I ² s / 4hO (1) (here, O: outer periphery, I: inner periphery, h: height, s: core saturation magnetization, k: orientation magnetic field) s is at most 2 Tesla (tes
la), and k is required to be about 1 Tesla, so that the mold height h at which a sufficient orientation can be obtained is as follows: h ≦ I ² / 2O (2) From the above, the height at which a uniform alignment magnetic field can be obtained is low when the inner circumference is small and the outer circumference is large, and if the mold height is set to a height of h or more, a magnetic field sufficient for radial alignment can not be obtained. I will. Therefore, it has been difficult to produce a long radial anisotropic magnet required for a high-performance motor. Therefore, in order to obtain a long radial anisotropic magnet,
A magnetic field is filled within the height h shown in the equation (2), which is sufficient for making the mold radially anisotropic in the mold shown in FIG. After a molded article having an orientation was obtained, a method of laminating a similar molded article in several layers was adopted. Examples of the method of laminating the compacts include a method of laminating a plurality of compacts and molding again, or a method of once performing molding at a predetermined height, moving the compact downward, and again applying the uniform magnetic field. There is a method of obtaining a laminated molded body by repeating the process of filling and molding the magnetic powder in the site where the above is obtained.

[0004]

In the case of R-Fe-B based sintered magnets, the compacts laminated by the above method or the like are defective because cracks are generated from the laminated boundaries in the subsequent sintering process. There are drawbacks such as lower yield and lower productivity. An object of the present invention is to solve such a drawback and to provide a production method in which a crack is not generated from the boundary of a laminated molded article, thereby increasing the yield and improving the productivity.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a rare-earth-rich alloy powder bonding layer is interposed at a boundary where cracks are likely to be generated, so that it is generated during sintering. Successfully controlling cracks
The present invention was completed by establishing various conditions. The abstract is R-
A radially anisotropic rare earth sintering characterized by sintering a compact formed by alternately compressing and laminating a Fe-B based rare earth magnet alloy powder layer and an alloy powder bonding layer having a composition richer in the rare earth than the alloy powder. It is in a method of manufacturing a magnet.

Hereinafter, the present invention will be described in detail.

The greatest feature of the present invention is that an alloy having a composition richer in rare earth than the alloy powder in order to strongly join R-Fe-B based rare earth magnet alloy (hereinafter referred to as A alloy) powder compacts. The powder layer (hereinafter referred to as R alloy) is interposed between the A alloy compacts as a bonding layer. This joining R alloy is an alloy comprising R as an essential element and at least one of Fe, Co and B, and R ₂ T ₁₄ B (T is Fe
Or Co) phase, R rich phase, RT ₄ B ₄ phase, RT ₃ phase,
RT ₂ phase, R ₂ T ₇ phase composed of one phase or two or more phases of RT ₅ phase. R is La containing Ce, Pr, Pr, Nd, Sm, Eu,
A mixed element of one or more selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu is used.
The melting points of these phases are from 500 ° C. to 1155 ° C., which prevent melting at the early stage of sintering and infiltration into the A alloy powder layer to generate cracks at boundaries between A alloy compacts. Further, since the R alloy is constituted by the elements contained in the A alloy, the magnetic properties do not deteriorate. Accordingly, a radially anisotropic sintered magnet having a large cylindrical height can be easily produced without causing cracks by interposing and laminating the R alloy powder between the A alloy compacts and sintering.

[0007] The composition range of the A alloy (R-Fe-B based rare earth magnet alloy) to which the present invention is applied is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb containing Y as the rare earth element R. , Dy, Ho, Er, Tm, Yb, and Lu, and is a mixed element composed of one or more elements, and is composed of Fe (Co can be substituted), B, and other additive elements.

Next, a method of preparing a rare earth alloy and a method of joining the same will be described. The alloy A is prepared by weighing the rare earth elements R, Fe and / or Co, other additional elements and B having a purity of 99.9% or more so as to have a predetermined atomic ratio, and melting and solidifying them in a high frequency furnace to produce an ingot. The ingot is roughly pulverized with a jaw crusher and further finely pulverized with a jet mill using N ₂ gas to obtain a fine powder having an average particle size of 1 to 5 μm. Separately, the R alloy for joining is prepared by weighing R, Fe, Co and B so as to have a predetermined atomic ratio, and producing an R alloy powder having an average particle size of 1 to 5 μm in the same manner as the A alloy powder.

Next, 1) A alloy powder is compression-molded to produce an A alloy compact (A1), 2) R alloy layer is used as a bonding layer and 3) A alloy compact (A2) is produced again A1
-The R-A2 compact is taken out and fired at 1000 to 1200C for 1 to 2 hours to obtain a radially anisotropic sintered magnet. For a long product, a molded product obtained by repeating the steps 1) and 2) may be sintered.

[0010] The magnetic field is formed by the following method. FIG.
(A), (b), (c), (d) and FIG. 4 are described in the order of steps in a die cross-sectional view of a radial magnetic field orientation press. The mold of FIG. 3 forms a molded body after being placed in the magnetic field molding apparatus of FIG. First, the raw material A alloy powder is supplied to the in-mold forming section 6 by the feeder 9 (FIG. 3A). Subsequently, when the upper punch 4 is moved down to just above the forming section 6, an orientation magnetic field until the core 2 reaches saturation is applied, and then compression molding is performed (FIG. 3B). Next, the compact 7 and the lower punch 3 are lowered to the non-magnetic die 1 '(FIG. 3C), and the R alloy powder 8 is laminated from above the compact 7 so as to have a predetermined height (FIG. 3D ))did. Next, as in FIG. 3A, the in-mold forming portion 6 is filled with the A alloy powder from the feeder 9 (FIG. 4), and is again formed under the same magnetic field and the same pressure.
2 A molded body is obtained. Further, the R alloy layer is laminated between the compacts A1 and A2 alone, and A1-RA2 is applied by applying an external pressure.
It is also possible to produce a molded body. Long object is this A1
-R-A2 Two molded bodies may be joined with an R alloy,
1-R-A2-RA-RA-A4 and the above steps 1) and 2) may be repeatedly laminated.

[0011]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1) (1) Production of R-Fe-B based rare earth magnet alloy (A alloy) powder: Nd, Dy, Fe, 99.9% purity, respectively.
Co, Al and B of 99.5% purity were converted to Nd 14.5-Dy 1.0-Fe.
It was weighed so as to have an atomic mixture ratio of 73.5-Co 3-Al 1.0-B 7.0 and melted and solidified in a high frequency furnace to produce an ingot. This ingot is coarsely crushed with a jaw crusher,
The powder was further pulverized by a jet mill using N ₂ gas to obtain a fine powder having an average particle size of 3.5 μm. (2) Production of rare earth rich alloy (R alloy for joining) powder: Nd, Fe, Co with purity of 99.9% and B with purity of 99.5% were mixed with Nd30-Fe23-Co40-B7.0 in atomic ratio. Weighed so as to form an ingot in the same manner as the alloy A,
A fine powder having an average particle size of 3.5 μm was obtained.

(3) Production of Radial Anisotropic Rare Earth Sintered Magnet: Next, a compact having a radial orientation in which A alloy powder and R alloy powder were laminated was prepared. 3 (a) to 3 (d)
4 and FIG. The A alloy powder is supplied to the in-mold forming section 6 by the feeder 9 (FIG. 3A).
Subsequently, the upper punch 4 is lowered, and when it descends to just above the in-mold forming section 6, an orientation magnetic field until the core 2 reaches saturation is applied. Thereafter, molding is performed at a pressure of 1 ton / cm ² (FIG. 3B). . Next, the compact 7 and the lower punch 3 are lowered to the non-magnetic die 1 '(FIG. 3 (c)), and R alloy powder is fed from above the compact 7 and stacked to a height of 1 mm (FIG. 3).
(D)). Thereafter, the in-mold forming portion 6 is again fed from the feeder 9.
Was filled with A alloy powder (FIG. 4), and molding was performed again under the same magnetic field and the same pressure. 4 in FIGS. 3A to 3D described above.
After repeating the process three times, the molded body 7 was extracted from the dies 1, 1 '. The dimensions of the molded body obtained in this way are 30.4 mm in outer diameter,
It was a cylinder with an inner diameter of 21.5 mm and a height of 18.0 mm. The compact was sintered at 1090 ° C. for 2 hours in a vacuum. No cracking was observed in the obtained radially anisotropic rare earth sintered magnet, and the joint portion (R alloy layer) had the same bending strength as the A alloy layer. The sintered magnet was further aged at 580 ° C. for 1 hour.
As shown in FIG. 5, cubic test pieces 12 of 2 mm × 2 mm × 2 mm were cut out from the obtained sintered magnet 11 one after another in the height direction. The test piece was magnetized with a pulse magnetic field of 5T, and then the magnetism was measured using a VSM (vibrating sample magnetometer). Table 1 shows the results. Here, 1 to 6 indicate positions when a cube 12 mm of 2 mm square is cut out from above the sintered magnet 11. From Table 1, it can be seen that the bonded sintered magnet has a long but uniform magnetic property.

(Comparative Example) A sintered magnet was obtained by molding the A alloy powder in two steps in the same manner as in the Example without using the R alloy powder for joining, but cracks were generated at the boundary of the molded body. It was accepted.

[0014]

[Table 1]

[0015]

According to the present invention, it is possible to stably produce a radially anisotropic sintered magnet having no cracks at the boundaries between the compacts, uniform in the height direction and excellent magnetic properties. The magnet is effective for high performance, high power, and downsizing of an AC servomotor, a DC brushless motor, a speaker magnet, and the like, and its use value in industry is extremely high.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a magnetic field forming unit used in the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of the magnetic field forming unit of FIG. 1;

FIGS. 3 (a), (b), (c) and (d) are explanatory views of a step of forming a radially anisotropic sintered magnet according to the present invention.

FIG. 4 shows a radially anisotropic sintered magnet according to the present invention.
It is explanatory drawing of the shaping process following (d).

FIG. 5 is an explanatory view showing a radially anisotropic sintered magnet of the present invention and a test piece cut out therefrom.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ferromagnetic die 1 'Non-magnetic die 2 Ferromagnetic core 3 Lower punch 4 Upper punch 5 Coil 6 Molding part 7 Molding 8 R alloy powder 9 Feeder 10 Radial magnetic field 11 Sintered magnet 12 Test piece ← Magnetic field lines

Claims (1)

(57) [Claims] 1. A radial formed body comprising an R-Fe-B rare earth magnet alloy powder layer and an alloy powder bonding layer having a composition richer in rare earth than the alloy powder are alternately compression-laminated and sintered. Manufacturing method of anisotropic rare earth sintered magnet.